Present day opto-electronic devices are constructed from materials that are capable of switching between two states, bit 0 and bit 1, either by the generation of electrons or magnetic fields. Recent advancements in optical technology resulted in the invention of compact-disk read-only memories (CD-ROM's) and magneto-optical read write memories (CDRW). The contemporary data storage media utilizes a two-dimensional design restricting them to serial data processing with a storage density of 12.5 million bytes per square centimeter. Numerous attempts have been made to formulate a three-dimensional memory device without success.
For example, U.S. Pat. No. 5,268,862 describes the use of an active photochromic material, spirobenzopyran in a polymeric matrix for use in 3D memory. The process of writing is a two photon process and requires the heterolytic cleavage of spirobenzopyran into a stable merocyanine complex. Reading of the data is initiated by the exposure of merocyanine to light, which causes fluorescence. Unfortunately, the photochemistry in this proposed 3D memory is not confined to a specific region, resulting in unwanted photochemical reactions in the adjacent cells outside the exposed area.
U.S. Pat. No. 5,253,198 describes the use of field-oriented bacteriorhodopsin in a polymer matrix. Orthogonally placed laser beams converge on the bacteriorhodopsin matrix to record a bit cell. A cleaning process is carried by actuating the two lasers non-simultaneously. The bit is read by actuating the lasers and reading the difference between bit 0 and bit 1 from the electric signal generated. One of the disadvantages to this matrix lies in the necessity to mechanically orient the memory cube relative to the lasers. This inadvertently causes unwanted side reactions in the adjacent bit cells.
U.S. Pat. No. 5,559,732 describes the branched photocycle memory architecture of bacteriorhodopsin for optical memories. The write process is a two-photon process, which involves a sequential one-photon route. U.S. Pat. Application Publication No 20060187795 A1 describes the creation of a 3D memory with the formation of a non-volatile state that is used in the read/write process.
Present day computational algorithms are limited in part by the lack of an efficient data storage media. To date, silicon-based memory chips are limited in their storage capacity and any improvements in this feature will become increasingly expensive. The persistent marketable force for smaller, faster and cheaper device components is pushing the existing technologies to their limits. This imposes the need for alternative technologies with economical storage/cost ratio to satisfy the proliferating demand for high throughput storage devices.
Bacteriorhodopsin-based protein optical memories offer great potential. These memories can be configured for thin-film photochromic, 3D branched-photocycle, holographic-binary or Fourier-transform holographic associative storage. The storage medium is lightweight, radiation hardened and relatively inexpensive, and combined with the inherent quantum efficiency and cyclicity of the protein, provides comparative advantages over present day organic and inorganic media. Nevertheless, the native protein is not optimal for any of the above-mentioned optical memories.
Therefore, what is needed is an alternative technology to silicon-based memory chips for the production of an inexpensive three-dimensional memory device having high through-put storage without adverse side reactions in adjacent bit cells.